Why not nitrogen instead of CO2?
 

One of the trendy things you can spend (waste) your money on in the automotive world is to have your tires pumped up with pure nitrogen. This is supposed to keep your tires inflated longer than regular air, and also supposedly has other benefits.

So I was wondering, since CO2 inflators have the opposite problem (CO2 leaks out faster than air, plus it's a greenhouse gas), why hasn't anyone made a portable nitrogen inflator system for bike tires? Is it purely cost, or is there some technical problem with bottling nitrogen in those little cartridges?

Search is your friend ;). For recent discussions on this subject, see these threads for example:

http://www.bikeforums.net/showthread.php?t=499922
http://www.bikeforums.net/showthread.php?t=579300
http://www.bikeforums.net/showthread.php?t=413043

--J

Thanks for the links. Dang, there goes my patent idea. :)

Much colder temperature. Much thicker container. Would require heavy gloves to handle the stuff. See Liquid Nitrogen - properties.

Briefly, a cylinder of the same size with the same amount of gaseous N2 as a 12 gm CO2 cylinder would be under about 8,500 psi. Do you want one of these in your pocket?

IIIRC from high school science class, air is 78% nitrogen.

dont worry about co2, just plant some more trees!

Or, get a frame pump. Then you dont need co2. Problem solved.

I agree that it is much more pricey than need be; but, in the truck, automotive and motorcycle realms, it really does offer cooler running, and more consistent pressure, under load and high speed.

Since air is 78% nitrogen, I don't understand how it can make that much difference, but, it does.

How about N2O instead? Then at least you could sniff your tire for a quick pain killer.

It only makes a difference because of the huge temperature differential caused by running at very high speeds and making turns at high g-loads for hundreds of miles.

So where does the CO2 in CO2 cartridges come from? Assuming that it comes from the air, we haven't added or subtracted anything by using it in our bike tires.

Planting trees is only a temporary solution. Eventually the trees will die and decompose, then all of the CO2 they hve absorbed during their lifespan will be reabsorbed into the atmosphere. It's kind of like storing it in a bike tire.

There are a zillion more important environmental issues than CO2 cartridges, but to evaluate the impact you'd have to look not only at where the gas comes from but also how it got compressed to 900 psi.

Commercially produced CO2 a biproduct of other processes such as ammonia production - so if they didn't collect it and put it in tanks, they'd just be bleeding it into the atmosphere (if it weren't for greenhouse gas emissions limitations). And compressing it involves electrical or gas-driven motors. Probably ought to include transportation costs to get the carts to your LBS too.

I've used about 12 carts in the last 5 years... my conscience is clear.

I think I was in one of those linked threads as a supporter of the nitrogen in tires following. I still have to say it works for me, and I am satisfied. I haven't put it in my bike tires yet, but plan to. It works great in my car tires. That pressure monitoring gizmo on the dash has not alerted me to a low tire pressure in over a year. Used to go off about every other week.

The liquid nitrogen thing requires clarification. When you pressurize any gas to high enough pressure, it will turn into a liquid. At very high pressure comes high temperature. This heat will be lost to the surroundings over time and a liquified pressurized gas will attain ambient temperature as long as the pressure remains constant. The problem would be when the pressure is released into a tire the heat that was lost must be replaced so the gas/liquid/container will become very cold; proportional to the pressue it was stored at. Liquid nitrogen converting back into a gas will be cpld enough to make a rubber tire freeze into something like black glass. Not good. Don't look for portable nitrogen inflators any time soon. Just not practical.

Having said that, gaseous nitrogen at 100psi would not have properties much different from air at 100psi. The benefit for tires is that nitrogen does not leak out as fast, does not oxidize the rubber, and most importantly, does not contain water vapor. The water vapor in air is probably what causes most of the problems. As a tire gets hot or cool the water vapor in the air makes the pressure fluctuate much more than nitrogen or dry air would.

Bike tires don't get nearly as hot as race car tires. Therein lies the reason that N2 in bike tires isn't that great of an idea.

Also, CO2 liquifies at a much higher temperature than any other easily attainable and safe gas, justifying its use in cartridges.

C'mon, guys, think about it ... the making of the tire itself is probably more has more enviromental impact than all the CO2 you could possibly use in a lifetime no matter how it's made.

As far as nitrogen in bike or car tires ... unless you're driving a Formula One race car, you're getting hosed. Please don't believe me .. do a quick search for "nitrogen tire scam" and read one of the million articles on why this is a waste by worthy sources.

Actually CO2 is a strange molecule on a few fronts. It goes from a liquid to a solid to a gas through what is called 'sublimation.' And it is the basis of why we breathe. One doesn't so much inhale air (N2 & O2) to get oxygen - that's part of it - but rather we need the O2 to react with C (carbon) in our bodies in order to excrete it. So CO2 is a waste product of humans and other mammals.

When I would buy Nitrogen gas for my chemistry lab at a school I taught at, it was in the form of compressed gas at a very high pressure. Buying it in it's liquid form required a wholly different set-up to contain it. But it had it's uses, too. Such as to prevent very sensitive molecules from decomposing. And using a banana to hammer nails into planks.

As for N2O - which is Nitrous Oxide - laughing gas - I knew a real genius who drove around with a tank of this in his car. One line from the tank went to his souped-up carb. while the other went in his mouth. He knocked out power for blocks when he hit the phone-pole. The police weren't laughing.

But you could look for them in the past. The cylinder mounted under the downtube of the 1958 Legnano racing bike shown here:
http://www.theracingbicycle.com/images/Gonfleur.JPG
is a gonfleur which reportedly was filled with compressed nitrogen gas (note: no liquid). Compared to CO2 cartridges, these needed to be much larger and at higher pressure since nitrogen doesn't liquify so easily and the cylinder just contained pressurized gas. So there's a considerable weight penalty and it would be lighter to carry a pump - but the refillable pressurized cylinder would allow for faster inflation.

If you are losing pressure across two weeks, you have a leak. One that isn't magically being fixed with N2. Car tires routinely hold pressure much, much better than this with just air.

Tubes are typically replaced much faster for other reasons than oxidation. If water was a problem, it would be because it was changing state from liquid/solid to gas. If it's always a gas, it is just like any other gas.

Holy moly! Hey that thing would be great for knocking a dog off or your leg.

CO2 cartridges are used for seltzer bottles, among other things. So there's already a massive factory or 10 making them, and making them in a size convenient for packaging onto a bicycle. Nitrogen, not so much, and the stations used by automotive tire shops use nitrogen packaged by the welding gas industry as a byproduct of their production of O2 and other gasses. Typically compressed nitrogen is used to pressurize underground cables to keep water from seeping in (the tanks you occasionally see chained to telephone poles). There's a big industry providing that gas already, the auto garages just take a little off that supply.

The gas in a CO2 cartridge isn't liquified. It's just compressed. You could take the same volume of any gas and compress it to the same PSI and fit it into the same cylinder. It's counter-intuitive. It's also science, by a guy named Avogadro a long time ago.

Science. It works.

I've been using NO2 for my tires.

Word to the wise: tubes with threadless stems are much gentler on your lips ;)

No you haven't. NO2 (technically N2O4) is Nitrogen Dioxide - a reddish-yellow gas that can kill you with one breath. A leak of this insidious poison did in 3 Soviet Cosmonauts some years back. They had just returned to Earth. When the ground-crew opened the capsule - all 3 were dead as doornails.

It is used as a rocket-fuel. Inhaled, it causes your lungs to fill with Nitric Acid and water - and you drown.

Sublimation is the process of changing from solid to gas without passing through a liquid phase. <sentence deleted d/t brainf art>

True, there's no liquid and that's why these are so much bigger than CO2 cartridges; a quantity of a liquid expands to 1,000 times (+/-) its volume as it evaporates to a gas. Gonfleurs were filled with compressed air, and since there's no liquid there would be no substantial advantage of using any gas other than air.

Only if you get it right. The CO2 does liquify when compressed and then occupies a much smaller volume in those little cylinders than it would at that pressure (about 900 psi) if it remained a gas and therefore followed the ideal gas law. Here are some comments from a company that makes the cartridges:
http://www.genuineinnovations.com/learn_about_co2.html

CO2 changes from liquid to solid. Then to gas. Solid CO2 is found widely used in many applications under the trade-name of Dry-Ice.

Do your homework. :D